The present invention relates generally to pumps adapted to pressurize fluids for hydraulic systems working with high pressure fluids. More particularly, the present invention relates to a supply pump which is adapted for incorporation into an accumulator-type fuel injection system.
In accumulator injector fuel injection systems such as disclosed in U.S. Pat. No. 4,566,416 entitled "ACCUMULATOR NOZZLE FUEL INJECTION SYSTEM" and assigned to the assignee of the present invention, a diesel engine drives a fuel pump which supplies fuel under a pressure to a fuel supply chamber. The pressurized fuel in the supply chamber is supplied to the fuel injectors of the engine for injection into the engine combustion chambers. Each of the accumulator injectors includes an accumulator chamber and a control chamber. Pressurized fuel in the control chamber is released for momentarily injecting a charge of fuel from the accumulator chamber. The fuel supply pump is continuously operated by the engine to supply fuel under pressure to the fuel supply chamber so that the fuel pressure within each injector may be restored to the supply pressure between fuel injection events.
It is accordingly a principal aim of the present invention to provide a new and improved fuel supply pump for continuously supplying fuel under a pressure to a storage chamber for delivery to the accumulator injectors of the associated engine. Included within the general aims of the present invention is the provision of a fuel supply pump of efficient construction which supplies a regulated pressure which is very responsive to changes in speed and fuel requirements of the associated engine.
Briefly stated, the invention in a preferred form is a fuel supply pump which comprises a housing enclosing a stator which forms a pump chamber, an axial supply bore connecting the pump chamber and a plurality of plunger bores opening into the pump chamber. A vane-type transfer pump is employed to transfer fuel from a fuel inlet through a supply passage to the pump chamber. A pressure regulator in communication with the supply passage acts to provide a substantially constant pressure to the fuel delivered to the pump chamber. A pump plunger is cooperatively reciprocable in each of the plunger bores to pressurize the fuel received in the pump chamber. An actuator ring which comprises a plurality of roller members mounted in fixed position is rotatable about the plungers to sequentially displace the plungers for reciprocation in the plunger bores. A rotor is rotatably received in the housing and adapted for being driven by the associated engine to rotate the actuator ring. An inlet metering valve is employed to meter the fuel supplied to the pump chamber. Pressurized fuel from the pump chamber is received by a fuel output bore for delivery to the injection system of the associated engine. A relief valve assembly comprises a relief chamber and a hydraulically controlled piston which is displaceable in the chamber to control the pressure of the fuel in the fuel output bore by selectively releasing fuel from the output bore.
In a preferred form of the invention, the inlet metering valve is a selectively positionable spool valve which is interposed in the supply passage. A solenoid or a stepper motor is employed to control the axial position of the metering valve. The opening pressure of the relief valve is also hydraulically controlled in response to the position of the metering valve.